CVE-2026-10103

published 2026-07-13

CVE-2026-10103: Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to verify post ownership in the shared channel inbound sync handler, which…

Priority P4 25 medium 4.3 CVSS 3.1

AV N AC L PR L UI N S U C N I L A N

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to verify post ownership in the shared channel inbound sync handler, which allows an authenticated remote cluster to modify or delete posts authored by local users or other remotes via crafted sync messages referencing arbitrary post IDs in channels shared with that remote.. Mattermost Advisory ID: MMSA-2026-00689

Affected

6 ranges

Vendor	Product	Version range	Fixed in
mattermost	mattermost	10.11.0 – 10.11.19	—
mattermost	mattermost	11.6.0 – 11.6.4	—
mattermost	mattermost	11.7.0 – 11.7.2	—
mattermost	mattermost_server	>= 10.11.0 < 10.11.20	10.11.20
mattermost	mattermost_server	>= 11.6.0 < 11.6.5	11.6.5
mattermost	mattermost_server	>= 11.7.0 < 11.7.3	11.7.3

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CWE-639